1. Field of the Invention
The present invention relates to an image taking device which is equipped in a camera such as a digital camera, and particularly relates to the image taking device which has the function to correct, or compensate, any possible image blur caused by a shake of a body of the camera, in which an image taking element is mounted movably in parallel with its light receiving surface.
2. Description of the Related Arts
An active compensation (or active correction) technology for compensating, or correcting, an image blur which may be caused by a misalignment of optical axis on the basis of a shake, in which the whole optical system or a part thereof is moved or swung, is generally divided into the following three types: a first type in which a compensation optical system is moved or swung, a second type in which an entire optical system is moved or swung, and a third type in which an image taking element is moved or swung. Of all the three types of image-blur compensators, the second type thereof is hardly put to practical use, not only because the member to be swung therein is large in mass and a large amount of energy is required for driving the member, but also because the volume of the member to be swung is large, thus increasing the overall size of the apparatus equipped with this type of image-blur compensator.
The third type thereof is disclosed, for example, in Japanese Laid-Open Patent Publication Nos. 9-116910 and 6-46314. The third type has many advantages like: few limitations put on design due to its optical sensitivity, a wide range of variations in which it is possible to apply this type to all kinds of lenses, and low cost. However, this type has disadvantages like: difficulty of maintaining the flatness of the plane to be moved or swung, and difficulty of processing the circuit board around the image taking element.
That is, in the third type of the image-blur compensator, the precision for detecting error(s) in movement must be higher as the number of pixels increases, and the mass and the amount in movement of the member to be moved or swung are apt to be larger in comparison with those of the type in which a lens is driven. This increases the area of the circuit board as a drive mechanism or driver, which results in an increase in the size of the image taking apparatus. The above problem is improved by separating the circuit board around the image taking element from the image taking element and by arranging it as a separate member. However, the signal outputted from the image taking element is weak or faint, and it is susceptible to noises picked up in the connection part.
Meanwhile, concerning the third type thereof, it is difficult to provide a construction, or structure, to prevent dust or foreign matter from entering thereinto, and it is therefore difficult to completely seal the image taking element. In other words, there has been a problem that the dust adheres to the surface of the image taking element, and that the dust itself is also photographed. The conventional image blur compensation mechanism (or image-blur compensator) in which the image taking element is swung or moved, does not include any countermeasure to solve this problem.
Meanwhile, Japanese Laid-Open Patent Publication No. 9-116910 discloses an image taking device in which high-frequency components of a subject (or an object) to be photographed are restricted prior to spatial sampling by the image taking element.
In this image taking device, the position of the image taking element is changed with respect to the position of the object image (or subject image) focussed on the image taking element during its exposure period of the image taking device so that two-dimensional spatial frequency characteristic is obtained, and so that its moire is reduced by diminishing deformation or distortion of the image by changing the frequency characteristic. That is, in the image taking device, the relative position of the image taking element to the focussing means can be changed. FIG. 1 of the same publication discloses a drive mechanism, or driver, for changing the position of the image taking element.
In the drive mechanism, the image taking element is disposed in a space defined by an L-shaped holding member, and one side of the holding member and one side of the image taking element are coupled together by a piezoelectric element so that the image taking element can be swung, or moved, in an X direction. In order to swing, or move, the holding member itself thus coupled to the image taking element in a Y direction perpendicular to the X direction, the other side of the holding member and a base are coupled together by a piezoelectric element. By applying a voltage having a waveform expressed by a trigonometrical function to each of the piezoelectric elements, the piezoelectric elements expand and contract, so that their movements are superimposed on each other. As a result, the image taking element is swung, or moved, circularly or elliptically.
However, according to the drive mechanism in which the image taking element is directly connected to a piezoelectric element as described above, the range of movement of the image taking element is extremely limited and small. Therefore, the drive mechanism cannot be employed as a mechanism for moving the image taking element over a wider range or greater distance, which is, for example, employed for correcting the misalignment of optical axis in order to compensate image blur possibly caused by an apparatus shaken manually. In order that the range of movement of the image taking element is larger, it cannot be helped that the drive mechanism must be also larger in size, which in turn leads to an image taking device, including the drive mechanism, of larger size.